I. Field of the Invention
The present invention relates to an apparatus for coupling optical signals into and out of an optical fiber through a moisture barrier layer thereof.
II. Description of the Prior Art
Optical fibers comprising an optical waveguide capable of transmitting light therein are used for transferring information in the form of light pulses, and a variety of means are known for injecting light into such optical fibers representative of the information to be transmitted as well as tapping light from such optical fibers for receiving such information. The most common type of devices for injecting light into, and for tapping light from, such optical fibers include means wherein the light is injected into an axial end face of a core of the waveguide, and means for receiving light from an opposite axial end face of the core of the waveguide. Such devices are disadvantageous in that termination of the waveguide is required to transmit or receive light.
Several devices are also known for injecting light into and tapping light from optical fibers through a side surface thereof so as not to require termination of the waveguide. In the case of devices for injecting light into a fiber which comprises a glass core, a glass cladding surrounding the core which together forms the optical waveguide or light guiding region, and a buffer which surrounds the cladding to protect both the cladding and core from moisture, it is common in the art to strip the buffer off of the optical fiber to facilitate injection or tapping of light into or from the core and cladding, and such a stripping practice is common with a variety of optical fiber taps, as evidenced by the teachings of Jeunhomme, U.S. Pat. No. 4,253,727; Goell, U.S. Pat. No. 3,982,123; Miller, U.S. Pat. No. 3,931,518; etc. Such devices are disadvantageous in that stripping the buffer off of the cladding exposes the cladding to moisture in the atmosphere which causes microcracks in the cladding to grow which rapidly deteriorates the strength of the optical fiber resulting in premature failure thereof.
In addition, through Cross, U.S. Pat. No. 4,270,839 describes a device wherein light can be tapped, as opposed to injected, from an optical fiber wherein the buffer can be retained thereon, the device described by Cross presents several additional disadvantages. In particular, according to the construction of this device, an optical fiber 1 is embedded within a slot contained in a light pipe 5, and the slot is subsequently filled with an epoxy solution which is cured to permanently bind the fiber within the light pipe. Thereafter, the fiber is bent in an area removed from the light pipe so as to convert core light modes into cladding and buffer light modes which are subsequently stripped therefrom by the light pipe 5 and epoxy 12. Such a construction requires the use of a relatively long light pipe 5, requires the use of an epoxy solution which potentially is toxic and can be spilled, and is furthermore not releaseable or easily adapted for in-the-field use.
Accordingly, a need exists in the art for an improved light coupler which can either inject light into or tap light from an optical fiber, or perform both light injecting and tapping functions, without removing any moisture barrier of the optical fiber, and which is releaseable and has a simplified construction.